Bridge on Mars

t’s not the work of fastidious Face on Mars engineers – but there’s a natural bridge on the red planet.A new batch of NASA Mars Reconnaissance Orbiter (MRO) imagery includes this inspection of the Tartarus Colles region.

MRO’s High-Resolution Imaging Science Experiment (HiRISE) camera has viewed a narrow trough running down the center of a valley that lies between two hills. Two trough segments terminate in blunt ends that are separated by a natural bridge or wall of material 75 feet (23 meters) wide.
It is likely that this trough formed as a lava tube and that its roof has mostly caved in over time, leaving only a small section standing.
Lava tubes are created when the top and sides of a “river” of lava freeze while molten rock continues to flow through its interior. After the eruption ceases, molten lava flows out of the tube leaving it empty. Tubes require a steady and sustained flow of lava to form, and they allow the lava to be transported a considerable distance without losing too much heat.
MRO’s super-powerful HiRISE images like this one are helpful in deciphering the various types of volcanism that have taken place on Mars.
Space.com